Mineral Nitrogen Fertilizer Research Articles

Abnormal shapes of production function: Model interpretations

An abnormal non-monotonic shape of production function (response of obtained yield to increasing rates of mineral nitrogen fertilizers) has been observed in experimental field trials. Often, the observed effect (an inflection point, or intermediate plateau or even local undershoot of the “yield-fertilization” curve) is treated as a test distortion and will be ignored or sorted out. This article presents the authors’ efforts to interpret and to explain similar phenomenon by means of investigating two mechanistic crop simulation models – AGROSIM and AGROTOOL. It is demonstrated that an imitation model can be used as a valuable tool of scientific research, allowing for the hypothesising of alternative understandings of non-trivial natural phenomena.

Influence of long-term fertilization on soil physicochemical properties in a brown soil

This study aims to explore the influence on soil physicochemical properties under a 38-y long-term fertilization in a brown soil. Soil samples (0-20 cm)were taken from the six treatments of the long-term fertilization trial in October 2016:no fertilizer (CK), N1(mineral nitrogen fertilizer), N1P (mineral nitrogen and phosphate fertilizer), N1PK (mineral nitrogen, phosphate and potassic fertilizer), pig manure (M2), M2N1P (pig manure, mineral nitrogen and phosphate fertilizer).The results showed thatthe long-term application of chemical fertilizers reduced soil pH value, while the application of organic fertilizers increased pH value. Fertilization significantly increased the content of AHN, TN and SOM. Compared with the CK treatment and chemical fertilizer treatments, organic fertilizer treatments significantly increased the content of AP and TP. The content of AK and TK were no significant difference in different treatment.

REPLACING NITROGEN FERTILIZATION BY USING ORGANIC AND BIOFERTILIZERS ON COSTATA PERSIMMON TREES.

The present study was conducted during 2015, 2016 and 2017 seasons to study the effect of replacing mineral nitrogen fertilization by organic nitrogen and biofertilizers on Costata persimmon trees, under calcareous soil conditions. The treatments consist of T1 (100% mineral nitrogen), T2 (75% mineral nitrogen + 25% organic nitrogen), T3 (50% mineral nitrogen + 25 % organic nitrogen + biofertilizer), T4 (25% mineral nitrogen + 50 % organic nitrogen + biofertilizer) and T5 (100% organic nitrogen). Rice straw compost was used as a source of organic nitrogen and N2-fixing free living bacteria namely Azotobacter chroococcum and Azospirillum lipoferum as a source of biofertilizers. The obtained results can be summarized as follows: Treatment of 50% mineral nitrogen + 25% organic nitrogen with biofertilizers gave the highest values of vegetative growth in terms of shoot number/branch, shoot length, leaf numbers per shoot and leaf area of Costata persimmon trees compared to mineral nitrogen fertilizers only. Moreover, treatments included organic and biofertilizers were raising leaf content values of chlorophyll, N, P, K, Ca, Fe, Mn and Zn especially in the second season. As for yield, treatment of 50% mineral nitrogen + 25% organic nitrogen + biofertilizer and 75 % mineral nitrogen + 25% organic nitrogen produced the highest yield in terms of number of fruits/tree, weight (kg/tree) and total yield (ton/feddan). All treatments led to improving properties of fruit quality especially treatment of 50% mineral nitrogen +25% organic nitrogen +biofertilizers. Also, treatments containing organic and biofertilizer led to reducing nitrate and nitrite values in fruit juice comparing with 100% mineral nitrogen fertilizer. Conclusively, this treatment is recommended: (50% mineral nitrogen +25% organic nitrogen +biofertilizers). This treatment gave the best growth, yield, fruit quality and nutritional status of Costata persimmon trees.

EFFECT OF WATER REQUIREMENTS AND NITROGEN FERTELIZATION ON MAIZE CROP PRODUCTIVITY IN CLAY SOIL

Field experiment was carried out at tractors and farm machinery testing &research station, Alex. Governorate, Egypt, during the summer season of 2017, to evaluate the effect of three levels of water requirements and two sources of nitrogen fertilization on the vegetation growth and yield of maize (zea maize L.) and some soil properties. The experiment included nine treatments which were arranged in a split plot based on RCBD design,and replicated three times. Main plotsconsisted of100% of water requirements for maize plant [100%WR], 80% of water requirements [80%WR] and 60% of water requirements [60%WR], while three fertilization types: Organic manure [OM] contains 120 unit’s organic nitrogen [ON], Mineral nitrogen fertilizer [MnF] contains 120 unit’s mineral nitrogen [MnN], Mixture of [OM] & [MnF] with proportion (1:1) contains 120 unit’s nitrogen [XOMn], as well as control were arranged in sub plots. Recommended fertilization was applied according to Agriculture ministry system. Measured parameters were number of rows in one ear, number of grains in each row, weight of 100- kernel (g), grain yield and stover yield (Ton/Fed). Statistical analysis of the experimental data indicated that, the treatment [80%WR]+ [XOMn] was the greatest significant of T-N, Av-N, EC,T-P, Kb and Av-W in comparing with all treatments. Addition [XOMn] and (80%WR) resulted inhigh significant values of number of rows in one ear, number of grains in each row, weight of 100- grain (g), grain yield and stover yield (kg/fed).

Successive impact of the nitrogen fertilization of basket willow (Salix viminalis L.) on the canopy architecture in 9th and 10th year of regrowth of shoots

The purpose of the present paper was an assessment of the successive impact of fertilization with nitrogen on the regrowth dynamics of the shoots of 10 genotypes (three clones and seven varieties) of basket willow (Salix viminalis L.) in the 9th and 10th year of cultivation. In 2008- 2015, mineral nitrogen fertilization was applied in the whole experiment in four doses. The measurements of height and thickness of willow shoots, of the quantity of live and dead shoots in the snag and live and dead snags on the plot were performed in the experiment realized in 2016-2017. Biometric measurements showed that increased mineral nitrogen fertilization in the year of its application intensified shoots growth in height and thickness, yet in the successive impact, in the 9th and 10th year of willow vegetation weakening of shoot regrowth in height and thickness is observed, and the number of live shoots in the snag and live snags on the plot have reduced. In particular, negative successive impact of the nitrogen fertilization on the willow canopy architecture was demonstrated on the objects that were mowed twice in the first 4-year rotation and on the varieties that do not tolerate this treatment.

QTL Identification and Mapping in Soft Spring Wheat (Triticum aestivum L.) under Controlled Agroecological and Biological Testing Area Conditions with and without Nitrogen Fertilizer

Quantitative trait loci (QTL) of agriculturally valuable traits of soft spring wheat (Triticum aestivum L.) were mapped in two simultaneous and independent experiments that were carried out in different agronomical backgrounds with respect to nitrogen availability (i.e., with and without introduction of a mineral nitrogen fertilizer) in order to reveal the effects of physiological and genetic interaction between the genotype and the environment. In total, 94 QTLs, which determine 31 physiologically and agriculturally important traits, have been identified. The connection between the loci identified and polymorphism by certain traits has been proven. The connection between the trait expression and introduction of the fertilizer has been confirmed by both correlation analysis and the single-factor analysis of variance. The analyses of QTL and correlation, as well as the single-factor analysis of variance, showed that 15 of 31 traits varied confidently. This shows that the expression of these traits depends on the presence of nitrogen nutrition. The data obtained are important for further study of physiological and genetic regulatory mechanisms of expression of the traits that were evaluated in the system of interaction between the genotype and the environment as well as for the marker-assisted selection of wheat.

Влияние азотных удобрений на урожайность и качество зерна сортов овса в условиях юга Нечерноземной зоны

The study was carried out in 2013-2015 in the Republic of Mordovia on leached medium deep heavy loam chernozem. In a field experiment the effect of pre-sowing application of mineral nitrogen fertilizers (N60) in combination with dressing-applied (N30) on yield and grain quality of covered varieties of oats (Gorizont, Krechet, Eclipse) was studied. The average yield of spring oat varieties without mineral fertilization varied from 2.58 to 2.84 t/ha. Early application of nitrogen mineral fertilizers under cultivation (N60) contributed to the increase in the seed productivity of spring oat varieties by 0.02-0.49 t/ha (Least Significant Difference LSD 0.5=0.12). The combination of pre-sowing application with dressing-applied nitrogen at the tillering stage (N30) led to increase in grain yield of spring oats by 0.18-0.43 t/ha (LSD 0.5=0.20) as compared to the variant without mineral fertilization. On the average in the experience the test weight of oat grain was 480-573 g/l. Nitrogen application for early-spring cultivation provided the increase of this index by 3-84 g/l (LSD 0.5 =6.5), mineral dressing at tillering stage - by 31-74 g/l (LSD 0.5=6.9) At the same time such parameters as the mass of 1000 grains and the degree of grain uniformity were not influenced by the rates of nitrogen fertilizers. Krechet variety proved to be the best among the cultivars studied. It showed almost as high seed productivity as standard Gorizont variety.

SOIL PHYSICAL QUALITY AFTER NITROGEN FERTILIZERS USE IN IRRIGATED PASTURE OF TIFTON 85

Tifton 85 ( Cynodon sp.) is a forage crop widely used for the voluminous production, but it has also the potential to promote preservation or improvement in soil structural quality, when well managed. The aim of this work was to evaluate the soil physical quality in a rotational grazing area of Tifton 85 under irrigation in Prudente de Morais, MG, Brazil, due to the application of mineral and organic nitrogen fertilizers. The treatments included different forms of N supply: 400 kg ha -1 of urea; 400 kg ha -1 of bovine manure; 400 kg ha -1 of urea and manure, in proportion 1:1 and the control, without nitrogen fertilization. The following soil physical quality indicators were determined in the layers 0.0-0.05 m and 0.05-0.10 m after two years of N application: water retention curve, total porosity, macroporosity, microporosity, soil bulk density, available water capacity, bulk soil air capacity, soil matrix air capacity and relative water capacity. There were differences among the treatments, in both layers. In general, the treatments using bovine manure promoted greater water storage and availability, which was related to the increase of the microporosity, due to the organic matter effect. However, these same treatments presented a relative compaction, which was associated to the maintenance of higher soil moistures. It was concluded that, even under the effects of intensive grazing, there was generally adequate soil physical quality, but a special attention is recommended to the soil susceptibility to compaction.

Environmental Effects over the First 2\xbd Rotation Periods of a Fertilised Poplar Short Rotation Coppice

A short rotation coppice (SRC) with poplar was established in a randomised fertilisation experiment on sandy loam soil in Potsdam (Northeast Germany). The main objective of this study was to assess if negative environmental effects as nitrogen leaching and greenhouse gas emissions are enhanced by mineral nitrogen (N) fertiliser applied to poplar at rates of 0, 50 and 75 kg N ha−1 year−1 and how these effects are influenced by tree age with increasing number of rotation periods and cycles of organic matter decomposition and tree growth after each harvesting event. Between 2008 and 2012, the leaching of nitrate (NO3−) was monitored with self-integrating accumulators over 6-month periods and the emissions of the greenhouse gases (GHG) nitrous oxide (N2O) and carbon dioxide (CO2) were determined in closed gas chambers. During the first 4 years of the poplar SRC, most nitrogen was lost through NO3− leaching from the main root zone; however, there was no significant relationship to the rate of N fertilisation. On average, 5.8 kg N ha−1 year−1 (13.0 kg CO2equ) was leached from the root zone. Nitrogen leaching rates decreased in the course of the 4-year study parallel to an increase of the fine root biomass and the degree of mycorrhization. In contrast to N leaching, the loss of nitrogen by N2O emissions from the soil was very low with an average of 0.61 kg N ha−1 year−1 (182 kg CO2equ) and were also not affected by N fertilisation over the whole study period. Real CO2 emissions from the poplar soil were two orders of magnitude higher ranging between 15,122 and 19,091 kg CO2 ha−1 year−1 and followed the rotation period with enhanced emission rates in the years of harvest. As key-factors for NO3− leaching and N2O emissions, the time after planting and after harvest and the rotation period have been identified by a mixed effects model.

Influence of Long-Term Fertilization on Spore Density and Colonization of Arbuscular Mycorrhizal Fungi in a Brown Soil

This study aims to explore changes of long-term fertilization on spore density and colonization of AMF (Arbuscular mycorrhizal fungi) under a 38-y long-term fertilization in a brown soil. Soil samples (0-20 cm,20-40cm,40-60cm)were taken from the six treatments of the long-term fertilization trial in October 2016:no fertilizer (CK), N1(mineral nitrogen fertilizer), N1P (mineral nitrogen and phosphate fertilizer), N1PK (mineral nitrogen, phosphate and potassic fertilizer), pig manure (M2), M2N1P (pig manure, mineral nitrogen andphosphate fertilizer).Spores were isolated from soils by wet sieving and sucrose density gradient centrifugation; mycorrhizal colonization levels were determined by the gridline intersect. The spore density was highest in the topsoils (0-20 cm), and was decreased with increasing of soil depth in each treatment. The spores density of M2N1P treatment was significantly higher than that of other treatments in each soil layer. Application of inorganic fertilizer (especially inorganic with organic fertilizer) can greatly improve the level of colonization. Our results suggested that long-term fertilization significantly affects spore density and colonization of AMF, however, spore density is not related to colonization rate.

SUPPLEMENTATION OF NUTRIENTS FOR TABLE BEETS BY IRRIGATION WITH TREATED DAIRY EFFLUENT

ABSTRACT: This study was conducted to evaluate the nutritional status of table beet plants cultivated in a greenhouse irrigated with treated dairy effluent at different irrigation depths. The experimental design used was a randomized block in a 3 x 3 + 1 factorial arrangement with four replications and conducted in a greenhouse. The treatments consisted of three types of water sources and three irrigation depths applied by drip irrigation: anaerobic effluent; anaerobic/aerobic effluent; tap water, and irrigation for replenishment 50; 100 and 150% of the crop evapotranspiration (ETc). All these treatments were applied in combination with 50% of the recommended nitrogen fertilization for the table beet cultivation. A control treatment was irrigated with tap water with irrigation depth equal to 100% ETc and received the complete dose (100%) of mineral nitrogen fertilizer. Table beet seedlings were arranged in 40 fiberglass boxes with a base area of 1 m2. Table beets were harvested 72 days after transplanting (DAT) when the leaves and roots were analyzed. Irrigation with wastewater promoted appropriate levels of macronutrients, distributed between the leaves and roots. The sodium was increased significantly in the leaves and roots of table beets in effluent treatments at increasing irrigation depths, which was antagonistic to the absorption of potassium.

Effect of Bio-Organic Additives and Mineral Nitrogen Fertilizer Rates on Nitrogen, Phosphorus and Potassium Uptake by Sorghum with Aid of 15N Stable Isotope

A pot experiment was conducted in the green house to evaluate the response of sorghum crop grown on newly reclaimed sand soil to different organic additives in combination with biofertilizer Azotobacter chroococcum and different rates of mineral-N. Straw and root dry weight was stimulated by bacterial inoculation combined with high rate of mineral fertilizer (40 mg N pot-1). Nitrogen uptake by straw and root was gradually increased with increasing fertilizer-N rates. Similar enhancement effect of organic fertilizers and bacterial inoculation was also recognized with high N rate. P uptake by plants was positively enhanced by nitrogen fertilizer application, compost and chicken manure additives. Reversibly, bacterial inoculation has no positive effect on P uptake by either straw or root. Potassium uptake was not varied as affected by organic additives. But, to some extent, it was enhanced by increasing the nitrogen fertilizer rates. Generally, bacterial inoculation has no positive effect on K uptake by either straw or root. Chicken manure was the best in releasing mineralized N (Ndforg) to inoculated plants, followed by leucaena residue then compost. In case of the un-inoculated plants, the release of N from chicken manure surpasses those of compost whereas leucaena residues came to the next. N derived from mineral fertilizer was significantly affected by mineral fertilizer rates and to some extent by organic types. Increases of %Ndff in the uninoculated plants confirmed its dependence mainly on N gained from mineral fertilizer rather than other sources like those derived from organic additives or soil.

Role of Foliar Spraying with Biostimulants Substances in Decreasing Mineral Nitrogen Fertilizer of Sugar Beet

In order to study the role of foliar spraying with biostimulants substances and fertilizing with nitrogen mineral fertilizer on productivity and quality of sugar beet, a field experiment was performed during 2015/2016 and 2016/2017 winter seasons at Tag Al-Ezz, Agricultural Research Station Farm, Dakahlia Governorate, Egypt. Strip-plot designs with four replicates were used. Spraying plants with 150 ml yeast extract/liter plus 1.5 ml humic acid/liter as mixture recorded the highest means of all studied characters. However, spraying with 150 ml yeast extract/liter came in the second rank, followed by spraying with 1.5 ml humic acid/liter, then spraying with water and lastly without (control treatment) in the two seasons. Decreasing mineral nitrogen fertilization from 100 to 85, 70 and 55% from the recommended dose (90 kg N/fed) caused gradual reduction in all studied characters, with exception sucrose and apparent purity in both seasons. Highest values of root, top and sugar yields per fed were recorded with adding 100 or 85 % from the recommended dose without significant differences between them during growing seasons. For maximizing sugar beet productivity and quality and decreasing environmental pollution and cost could be succeeded with spraying plants twice with the mixture of 150 ml yeast extract/liter plus 1.5 ml humic acid/liter and fertilizing with 76.5 kg N per fed as soil application under environmental conditions of Dakahlia Governorate, Egypt.

Effect of combined application of organic and mineral nitrogen and phosphorus fertilizer on soil physico-chemical properties and grain yield of food barley (<i>Hordeum vulgare L.</i>) in Kaffa Zone, South-western Ethiopia

Low soil fertility is one of the major factors limiting the yield of barley in Kaffa Zone, south-western Ethiopia. The problem is more severe in the Zone due to soil erosion and nutrient leaching caused by heavy and continuous rainfall. Thus, field experiment was conducted to assess the effect of combined organic and mineral nitrogen (N) and phosphorus (P) on selected soil physico-chemical properties and on grain yield of food barley in Ghimbo and Adiyo districts, south-western Ethiopia. Fourteen treatments comprising two organic fertilizer rates, i.e. 2.5 and 5 t ha −1 of Farm Yard Manure (FYM) and Vermicomost (VC) combined with three levels of mineral NP (25, 50 and 75% of recommended rates of NP), 100% recommended rate of inorganic NP (23 kg N ha -1 and 46 kg P 2 O 5 ha -1 ) and no fertilizer application (control) in randomized complete block design on clay soil in Ghimbo and clay loam soil in Adiyo with three replications. Results indicated that the application of FYM in combination with different levels of recommended rates of inorganic N and P significantly improved most of the soil physico-chemical properties and significantly increased the grain yield of food barley over the application of 100% mineral NP alone and the control. The application of 5 t FYM ha −1 in combination with 75% recommended rates of inorganic N and P (17.25 kg N ha −1 and 34.5 kg P 2 O 5 ha −1 ) was found to be superior and increased soil organic carbon content by 36 and 44.6%, available P by 70.5 and 78.2%, available K by 42.5 and 26.3%, and increased yield of barley by 76.8 and 83.5% in Adiyo and Ghimbo, respectively, over the application of 100% recommended rate of inorganic N and P only. Therefore, it can be concluded and recommended that the application of 5 t FYM ha −1 in combination with 75% of the recommended rates of inorganic N and P (17.25 kg N ha −1 and 34.5 kg P 2 O 5 ha −1 ) can improve soil fertility and can increase yield of food barley in the study area. Keywords: Farmyard manure, Nitrogen, Phosphorous, Vermicompost, Ethiopia.

Changes in Soil Aggregate Stability Induced by Mineral Nitrogen Fertilizer Application

The stability of soil aggregates is one of the most important characteristics of the soil affecting the overall soil quality and its health. In locality Březová nad Svitavou, experiment to reveal the effect of nitrogen dose on the stability of soil aggregates of Rendzina soil was carried out. The aim was to detect changes in soil aggregate stability after 4 and 5 years from the beginning of the experiment. There were tested 7 variants, prepared in triplicate. The results revealed that the stability of soil aggregates decreases with increasing amounts of applied N. Effect of N application was not statistically significant in the fourth but in the fifth year of the experiment. The results also revealed a significant deterioration in the stability of soil aggregates in the fifth year compared to the fourth year of the experiment.

Simulating soil carbon sequestration from long term fertilizer and manure additions under continuous wheat using the DailyDayCent model

The widely used ecosystem model DailyDayCent (DDC) was used to predict soil organic carbon (SOC) sequestration and yield under different fertilization treatments on a wheat (Triticum aestivum) monoculture on Broadbalk field, Rothamsted, UK. Over a period of about 170 years, the management practices on the test site, which is separated into plots with different treatments of fertilizer and manure application, are well documented. Four treatments consisting of control (no fertilizer), mineral nitrogen (N) fertilizer (MN), farm yard manure (FYM) and a combination of both (FYMN) have been selected for the study. DDC simulated the greatest increases in SOC (three times higher compared to simulation of the control plot) in the FYM plot. Overall a good agreement between modelled and measured yield was obtained (except in control plots). As observed in the experimental plots, the highest yield predicted by the model is with FYMN plot (more than three times higher relative to the control plot). A sensitivity test for the MN and FYM plots demonstrated that predicted SOC was relatively insensitive (1%) to bulk density, pH and field capacity. Higher sensitivity (4–7%) of predicted SOC changes were observed by changes in external C input. An increase of temperature by 1 °C or precipitation by 10% decreased predicted SOC by 2–4% and vice versa, and simulated a 1–4% variability in yield. DDC is a useful tool for simulating SOC in the long term plots, with a good fit to data, and is useful for examining alternate hypotheses of yield and SOC responses.

Alternative Fertility Management for Establishing New Apple Orchards in the Mid-Atlantic

In the Mid-Atlantic, mineral nitrogen (N) fertilizers are applied in high-density apple (Malus ×domestica Borkh.) orchards to increase tree vegetative growth and achieve earlier fruiting. However, when applied in excess of plant needs, N fertilizer applications are an unnecessary expense and may lead to N leaching and groundwater pollution. Therefore, it is necessary to develop orchard fertilization programs that simultaneously provide adequate crop nutrition and minimize N loss into the environment. Nitrogen was applied in each of 3 years to newly planted ‘Red Delicious cv Schlect’/‘M.26’ trees at 67 kg N/ha/year in six fertilizer treatments: 1) two equal applications of granular calcium nitrate [Ca(NO3)2]; 2) chicken litter compost; 3) yardwaste compost; 4) a combination of chicken litter compost and granular Ca(NO3)2 with equal amounts of N from each fertilizer; 5) a combination of yardwaste compost and granular Ca(NO3)2 with equal amounts of N from each fertilizer; and 6) fertigation which consisted of eight weekly applications of solubilized Ca(NO3)2. Nonfertilized trees served as the control. In the third year of this experiment, the two chicken litter compost treatments had the greatest soil extractable P, the yardwaste compost treatment had the greatest soil extractable K, both full-rate compost treatments had greater soil extractable Mg than the other treatments, and all four compost treatments had greater soil extractable Mn than the treatments without compost. The four compost treatments also had greater soil extractable Ca and B than treatments without compost. By the third year of the experiment, the four compost treatments also had greater soil organic matter (OM) and soil C (with the integrated chicken litter compost treatment having similar soil C to the other treatments). Potentially mineralizable nitrogen and soil microbial biomass were similar among the treatments over the course of this experiment. The full rate chicken litter compost treatment and both yardwaste compost treatments had greater soil microbial respiration in 2015. The fertigation treatment performed similarly to the treatment where Ca(NO3)2 was applied as a granular product to the soil. Treatment differences found for the soil properties did not translate to increased tree size or leaf N content, suggesting that the trees were able to acquire sufficient N from the soil under all of the treatments. Our results suggest that applying fertilizers to fine textured soil with relatively high OM may not increase apple tree growth or productivity within the first 3 years after planting. In addition, compost applications can improve many soil properties, but these differences may not result in improved orchard productivity within 3 years.

Long‐Term Effects of Mineral Nitrogen Fertilizer on Irrigated Maize and Soil Properties

Core Ideas Grain yield, biomass, N uptake, SPAD units, soil N levels and N efficiciencies were affected by the N application rate. Maximum grain yields required 203 kg N ha−1 of available N in the 0‐ to 30‐cm layer soil. Sampling to a depth of 0 to 30 cm provided similar correlations than sampling to 0 to 60 and 0 to 90 cm. Mineral N fertilization increased soil organic C stock. Nitrogen is a key determinant of growth and grain yield (GY) in maize (Zea mays L.) and is therefore economically and environmentally important. We investigated the performance of maize crops in a 12‐yr experiment (2002–2007, 2010–2015) under sprinkler irrigation in a petrocalcic calcixerept soil in northeastern Spain, with controlled mineral N application rates (0, 100, 150, 200, 250, 300, and 400 kg N ha−1 yr−1). The application rate affected maize GY, biomass, N uptake, SPAD units, soil N levels, N efficiencies, and soil organic carbon (SOC). Average maximum GY's (∼15 Mg ha−1) required 203 kg N ha−1 of available N (defined as initial soil NO3− plus N fertilizer) in the 0‐ to 30‐cm horizon, confirming the importance of the soil N content. Nitrate levels in the 0‐ to 30‐cm horizon for maximum yields achieved a R2 value in the plateau fitting model similar to the 0‐ to 60‐ and 0‐ to 90‐cm horizons. The GY's increased at a rate of 192 kg ha−1 yr−1, suggesting a combination of genetic improvement in the hybrids and also an improvement in agronomic management. The 200 kg N ha−1 fertilizer treatment achieved almost the highest GY's (∼14 Mg ha−1) with simultaneous high nitrogen use efficiency (NUE) (0.83 kg kg−1). Mineral N fertilization also increased the stock of SOC in the 0‐ to 30‐cm horizon.

Why organic resources and current fertilizer formulations in Southern Africa cannot sustain maize productivity: Evidence from a long-term experiment in Zimbabwe

Sustainability of maize-based cropping systems is a major challenge for southern Africa, yet the demand for maize as staple food and animal feed in the region continues to increase. A study was conducted on a sandy clay loam (220 g clay kg-1 soil) at Domboshawa in Zimbabwe to investigate the long-term effects of organic resource quality and application rate, and nitrogen (N) fertilization on soil chemical properties and maize (Zea mays L.) productivity. Crotalaria juncea (high quality), Calliandra calothyrsus (medium quality), cattle manure (variable quality), maize stover and Pinus patula sawdust (both low quality) were incorporated into soil at 4.0 t C ha-1 (high rate) and 1.2 t C ha-1 (low rate) at the start of each cropping season for nine consecutive years. At both high and low application rates, each of the five organic resources was applied in combination with or without mineral nitrogen (N) fertilizer at 120 kg N ha-1. The nine-year period saw maize grain yields declining by 22% to 84% across treatments despite increases in soil organic carbon, total N and available P from 6% to 80%. Crotalaria, Calliandra and manure led to a less steep yield decline. Exchangeable calcium (Ca), magnesium (Mg) and potassium (K), and soil pH explained much of the variation in yield patterns observed under the different organic resource applications. Maize grain yield was positively correlated with exchangeable Ca (r = 0.51), Mg (r = 0.62) and K (r = 0.53), and soil pH (r = 0.49), but negatively correlated with other soil properties over the 9-year period. We concluded that declining soil exchangeable basic cations were the underlying causes of decreasing maize productivity, and was aggravated by use of low rates of organic resource inputs, particularly with N fertilization. Current nutrient management and fertilizer recommendations that emphasize inorganic N, P and K significantly undervalue the role played by organic resources in sustainability of maize cropping systems in southern Africa.

Influnce of Integration between Mineral Nitrogen and Humic Acid Fertilizers on Producivity and Nitrogen Partitioning Dynamic in Maize Plants

Two field experiments were carried out in Agric. Expt. Farm, Fac. of Agric., Ain Shams Univ. at Shalakan, Kalubia Governorate, Egypt during 2014 and 2015 growing seasons. These experiments aimed to study the effect of integrated between mineral nitrogen fertilizer (60, 90 and 120 kg / fad) and Humic acid (0, 15 and 20 kg / fad) on productivity and nitrogen partitioning dynamic of maize (zea maize) plants: Plants treated with120 kg MN/fad + 20 kg HA and 120 kg MN/fad + 15 kg HA gave the highest values of ear weight (264.9 and 257.4 g), shelling percentage(85.37 and 84.67 % ),plant height (284.2 and 279.7 cm), 100 kernel weight (40.20 and 39.09 g),stover yield (9.33 and 9.13 ton/fad) and biological yield (13.10 and 12.66 ton/fad) respectively. Maximum grain yield (3.76 ton/fad) was obtained when plants were fertilized with 120 kg MN. + 20 kg HA. Meanwhile, the lowest value (1.98 ton/fad) was recorded when plants were fertilized with 60 kg MN. Results also showed that grain nitrogen (%), stover nitrogen %, biological nitrogen %, grain nitrogen yield (kg/fad), stover nitrogen yield (kg/fad), total nitrogen yield (kg/fad), GCP % and GCPY (kg/fad) were significantly the highest due to fertilization with 120 kg MN/fad + 20 kg HA/fad. Such potent treatment increased the previous traits by 1.723%, 0.413%, 2.14%, 64.94 (kg/fad), 38.58 (kg/fad), 103 (kg/fad), 9.82 % and 370.2 (kg/fad), respectively. Data also cleared that the effect of integration between mineral nitrogen fertilizer and humic acid were significantly differed in NUE, NRE%, NPF and NHI%.